Multi-Layer Ceramic Capacitor

ABSTRACT

A multi-layer ceramic capacitor having a weight of 8 mg or more includes a capacitance forming unit and a protective unit. The capacitance forming unit includes internal electrodes that are laminated in a first direction and includes end portions, positions of the end portions in a second direction orthogonal to the first direction being aligned with one another within a range of 0.5 μm in the second direction. The protective unit covers the capacitance forming unit in the first direction and the second direction and includes an outer surface, a shortest distance between the outer surface and the end portion of an outermost layer in the internal electrodes in the first direction exceeding 10 μm.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119 of JapaneseApplication No. 2017-240796, filed Dec. 15, 2017, which is herebyincorporated in its entirety.

BACKGROUND

The present disclosure relates to a large-size multi-layer ceramiccapacitor.

Japanese Patent Application Laid-open No. 2001-6964 discloses alarge-size multi-layer ceramic capacitor. Such a large-size multi-layerceramic capacitor enables increase in capacitance by enlarging theintersectional area of internal electrodes or increasing the number oflamination. This allows the multi-layer ceramic capacitor to be used inplace of an electrolytic capacitor, for example.

SUMMARY

However, the weight of the multi-layer ceramic capacitor increases alongwith increase in size thereof. Accordingly, a large impact is given tothe large-size multi-layer ceramic capacitor by the self-weight evenwhen the large-size multi-layer ceramic capacitor drops from the heightof approximately several centimeters at the time of manufacturing,mounting, or the like. Therefore, the large-size multi-layer ceramiccapacitor is likely to crack.

In the multi-layer ceramic capacitor having cracks, when moisture thathas infiltrated into the cracks from an external environment reaches theinternal electrodes, sufficient insulation properties between theinternal electrodes may be difficult to ensure. Therefore, themulti-layer ceramic capacitor has difficulty in ensuring the moistureresistance along with the increase in size.

In view of the circumstances as described above, it is desirable toprovide a multi-layer ceramic capacitor having both of high moistureresistance and a large capacitance.

According to an embodiment of the present disclosure, there is provideda multi-layer ceramic capacitor having a weight of 8 mg or more andincluding a capacitance forming unit and a protective unit.

The capacitance forming unit includes internal electrodes that arelaminated in a first direction and includes end portions, positions ofthe end portions in a second direction orthogonal to the first directionbeing aligned with one another within a range of 0.5 μm in the seconddirection.

The protective unit covers the capacitance forming unit in the firstdirection and the second direction and includes an outer surface, ashortest distance between the outer surface and the end portion of anoutermost layer in the internal electrodes in the first directionexceeding 10 μm.

In this configuration, since the positions of the end portions of theinternal electrodes are aligned with one another, the internalelectrodes can be appropriately protected also by the protective unithaving a small thickness. Therefore, in this configuration, it ispossible to reduce the thickness of the protective unit and enlarge theintersectional area of the internal electrodes as much. With thisconfiguration, increase in capacitance can be achieved without involvingincrease in size. In such a manner, this configuration does not causethe increase in weight by the increase in capacitance. Thus, cracks areless likely to be generated.

Further, in this configuration, the shortest distance between the outersurface of the protective unit and the end portion of the outermostlayer in the internal electrodes exceeds 10 μm. In other words, in theprotective unit, the thickness is sufficiently ensured at the ridge thatcovers the vicinity of the end portion of the outermost layer in theinternal electrodes. Accordingly, even if a crack is generated in theridge of the protective unit due to an impact at dropping, moisture thathas infiltrated into the crack is less likely to reach the internalelectrodes.

In such a manner, in this multi-layer ceramic capacitor, cracks are lesslikely to be generated and moisture resistance is less likely to beimpaired even if cracks are generated.

The outer surface of the protective unit may have an exposure dimensionof 1 mm or more in a third direction orthogonal to the first directionand the second direction.

In this configuration, the exposure dimension of the outer surface ofthe protective unit is large and an impact is easily applied to theprotective unit, but moisture resistance is less likely to be impairedby the configuration described above.

The number of lamination of the internal electrodes may be 500 layers ormore.

In this configuration, the multi-layer ceramic capacitor having a largecapacitance is further obtained.

It is possible to provide a multi-layer ceramic capacitor having both ofhigh moisture resistance and a large capacitance.

These and other objects, features and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription of embodiments thereof, as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a multi-layer ceramic capacitoraccording to an embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of the multi-layer ceramic capacitortaken along the A-A′ line in FIG. 1;

FIG. 3 is a cross-sectional view of the multi-layer ceramic capacitortaken along the B-B′ line in FIG. 1;

FIG. 4 is a flowchart showing a method of producing the multi-layerceramic capacitor;

FIG. 5 is a perspective view of a multi-layer unit produced in Step S01of the production method described above;

FIG. 6A is a cross-sectional view schematically showing Step S03 of theproduction method described above;

FIG. 6B is a cross-sectional view schematically showing Step S03 of theproduction method described above;

FIG. 7 is a partially enlarged cross-sectional view of a region V of themulti-layer ceramic capacitor shown in FIG. 3;

FIG. 8A is a partial cross-sectional view showing a modified example ofthe multi-layer ceramic capacitor;

FIG. 8B is a partial cross-sectional view showing a modified example ofthe multi-layer ceramic capacitor;

FIG. 8C is a partial cross-sectional view showing a modified example ofthe multi-layer ceramic capacitor;

FIG. 9A is a graph showing evaluation results of Examples andComparative examples; and

FIG. 9B is a graph showing evaluation results of Examples andComparative examples.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be describedwith reference to the figures.

In the figures, an X axis, a Y axis, and a Z axis orthogonal to oneanother are shown as appropriate. The X axis, the Y axis, and the Z axisare common in all figures.

1. OVERALL CONFIGURATION OF MULTI-LAYER CERAMIC CAPACITOR 10

FIGS. 1 to 3 each show a multi-layer ceramic capacitor 10 according toan embodiment of the present disclosure. FIG. 1 is a perspective view ofthe multi-layer ceramic capacitor 10. FIG. 2 is a cross-sectional viewof the multi-layer ceramic capacitor 10 taken along the A-A′ line inFIG. 1. FIG. 3 is a cross-sectional view of the multi-layer ceramiccapacitor 10 taken along the B-B′ line in FIG. 1.

The multi-layer ceramic capacitor 10 has a configuration of a largecapacitance and a large size with the weight of 8 mg or more. Typically,the multi-layer ceramic capacitor 10 has a dimension of approximately1.6 to 5.7 mm in the X-axis direction and dimensions of approximately0.8 to 5.0 mm in the Y- and Z-axis directions. Further, typically, thecapacitance of the multi-layer ceramic capacitor 10 is approximately 100to 1,000 μF.

The multi-layer ceramic capacitor 10 can be widely used in useapplications expected for a large capacitance and is typically used in ause application in which an electrolytic capacitor is used. As anexample, the multi-layer ceramic capacitor 10 can be used in place of anelectrolytic capacitor that is widely used in stationary devices formobile communications.

The multi-layer ceramic capacitor 10 includes a ceramic body 11, a firstexternal electrode 14, and a second external electrode 15. Typically,the ceramic body 11 is formed as a hexahedron having two main surfacesfacing in the Z-axis direction, two side surfaces facing in the Y-axisdirection, and two end surfaces facing in the X-axis direction.

The first external electrode 14 and the second external electrode 15cover the end surfaces of the ceramic body 11 and face each other in theX-axis direction while sandwiching the ceramic body 11 therebetween. Thefirst external electrode 14 and the second external electrode 15 extendto the main surfaces and the side surfaces from the end surfaces of theceramic body 11. With this configuration, both of the first externalelectrode 14 and the second external electrode 15 have U-shaped crosssections parallel to the X-Z plane and the X-Y plane.

It should be noted that the shapes of the first external electrode 14and the second external electrode 15 are not limited to those shown inFIG. 1. For example, the first external electrode 14 and the secondexternal electrode 15 may extend to one of the main surfaces from theend surfaces of the ceramic body 11 and have L-shaped cross sectionsparallel to the X-Z plane. Further, the first external electrode 14 andthe second external electrode 15 may not extend to any of the mainsurfaces and the side surfaces.

The first and second external electrodes 14 and 15 are each formed of agood conductor of electricity. Examples of the good conductor ofelectricity forming the first and second external electrodes 14 and 15include a metal or alloy mainly containing copper (Cu), nickel (Ni), tin(Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or thelike.

The ceramic body 11 is formed of dielectric ceramics and includes amulti-layer unit 16 and side margins 17. The multi-layer unit 16 has twomain surfaces M facing in the Z-axis direction and two side surfaces Sfacing in the Y-axis direction. The side margins 17 cover the two sidesurfaces S of the multi-layer unit 16.

The multi-layer unit 16 has a configuration in which a plurality of flatplate-like ceramic layers extending along the X-Y plane are laminated inthe Z-axis direction. The multi-layer unit 16 includes a capacitanceforming unit 18 and covers 19. The covers 19 cover the capacitanceforming unit 18 vertically in the Z-axis direction and constitute thetwo main surfaces M of the multi-layer unit 16.

The capacitance forming unit 18 includes a plurality of first internalelectrodes 12 and a plurality of second internal electrodes 13 that aredisposed between the plurality of ceramic layers. The first and secondinternal electrodes 12 and 13 each have a sheet-like shape extendingalong the X-Y plane. The first and second internal electrodes 12 and 13are alternately disposed along the Z-axis direction. In other words, thefirst internal electrode 12 and the second internal electrode 13 faceeach other in the Z-axis direction while sandwiching the ceramic layertherebetween.

The first and second internal electrodes 12 and 13 are formed over theentire width of the capacitance forming unit 18 in the Y-axis directionand are exposed at both the side surfaces S of the multi-layer unit 16.In the ceramic body 11, the side margins 17 that cover both the sidesurfaces S of the multi-layer unit 16 ensure insulation propertiesbetween the first internal electrodes 12 and the second internalelectrodes 13, which are adjacent to each other in both the sidesurfaces S of the multi-layer unit 16.

The covers 19 and the side margins 17 cover the capacitance forming unit18 in the Y- and Z-axis directions to be configured as a protective unit20 that protects the capacitance forming unit 18. The protective unit 20has a function of protecting the capacitance forming unit 18 from animpact given to the ceramic body 11 when the multi-layer ceramiccapacitor 10 drops at the time of manufacturing or mounting, forexample.

Since the multi-layer ceramic capacitor 10 has a configuration of alarge size with the weight of 8 mg or more, a large impact is giventhereto by the self-weight when the multi-layer ceramic capacitor 10drops. As a result, in the multi-layer ceramic capacitor 10, a crackeasily occurs in the protective unit 20. When the crack reaches thefirst internal electrodes 12 and the second internal electrodes 13,insulation properties between the first internal electrodes 12 and thesecond internal electrodes 13 are reduced due to moisture of theexternal environment.

It is known that a crack is easily generated particularly when theimpact energy of 3.0*10⁻⁶ J or more is applied to the multi-layerceramic capacitor 10. This impact energy corresponds to the energy whena multi-layer ceramic capacitor 10 of 10 mg drops from the height of 3cm and collides with another multi-layer ceramic capacitor 10.

Further, in the multi-layer ceramic capacitor 10, as a dimension of theouter surface of the protective unit 20 in the X-axis direction, whichis exposed without being covered with the first and second externalelectrodes 14 and 15, i.e., an exposure dimension becomes larger, animpact is more likely to be given to the protective unit 20.Specifically, when the exposure dimension of the outer surface of theprotective unit 20 is 1 mm or more, or further 2.5 mm or more, a crackis easily generated particularly in the protective unit 20.

The protective unit 20 of the multi-layer ceramic capacitor 10 accordingto this embodiment has a configuration in which moisture resistance isless likely to be impaired even if a crack is generated when themulti-layer ceramic capacitor 10 drops at the time of manufacturing,mounting, or the like. The configuration in which moisture resistance ofthe protective unit 20 is less likely to be impaired will be describedlater in detail in the “Detailed Configuration of Protective Unit 20”.

The first internal electrodes 12 are drawn to one of the end portions ofthe ceramic body 11. The second internal electrodes 13 are drawn to theother end portion of the ceramic body 11. With this configuration, thefirst internal electrodes 12 are connected to only the first externalelectrode 14, and the second internal electrodes 13 are connected toonly the second external electrode 15.

With such a configuration, when a voltage is applied between the firstexternal electrode 14 and the second external electrode 15 in themulti-layer ceramic capacitor 10, the voltage is applied to theplurality of ceramic layers between the first internal electrodes 12 andthe second internal electrodes 13. With this configuration, themulti-layer ceramic capacitor 10 stores charge corresponding to thevoltage applied between the first external electrode 14 and the secondexternal electrode 15.

In the ceramic body 11, in order to increase capacitances of the ceramiclayers provided between the first internal electrodes 12 and the secondinternal electrodes 13, dielectric ceramics having a high dielectricconstant is used. For the dielectric ceramics having a high dielectricconstant, for example, a material having a Perovskite structurecontaining barium (Ba) and titanium (Ti), which is typified by bariumtitanate (BaTiO₃), is used.

It should be noted that the ceramic layer may be formed of a strontiumtitanate (SrTiO₃) based material, a calcium titanate (CaTiO₃) basedmaterial, a magnesium titanate (MgTiO₃) based material, a calciumzirconate (CaZrO₃) based material, a calcium zirconate titanate(Ca(Zr,Ti)O₃) based material, a barium zirconate (BaZrO₃) basedmaterial, a titanium oxide (TiO₂) based material, or the like.

The first and second internal electrodes 12 and 13 are each formed of agood conductor of electricity. Examples of the good conductor ofelectricity forming the first and second internal electrodes 12 and 13typically include nickel (Ni), and other than nickel (Ni), include ametal or alloy mainly containing copper (Cu), palladium (Pd), platinum(Pt), silver (Ag), gold (Au), or the like.

It should be noted that FIGS. 2 and 3 each show eight layers of thefirst and second internal electrodes 12 and 13 in total, which is muchsmaller than the actual number of laminated layers, for the purpose offacilitating visualization of the laminated structure. However, in themulti-layer ceramic capacitor 10, it is favorable that the total numberof first and second internal electrodes 12 and 13 to be laminated is 500layers or more in order to obtain a large capacitance as describedabove.

Further, the basic configuration of the multi-layer ceramic capacitor 10according to this embodiment is not limited to the configuration shownin FIGS. 1 to 3 and can be changed as appropriate. For example, theshapes of the ceramic body 11 and the first and second externalelectrodes 14 and 15 can be determined as appropriate according to thesize and performance expected for the multi-layer ceramic capacitor 10.

2. METHOD OF PRODUCING MULTI-LAYER CERAMIC CAPACITOR 10

FIG. 4 is a flowchart showing a method of producing the multi-layerceramic capacitor 10. FIGS. 5, 6A, and 6B are views each schematicallyshowing a production process of the multi-layer ceramic capacitor 10.Hereinafter, the method of producing the multi-layer ceramic capacitor10 will be described according to FIG. 4 with reference to FIGS. 5, 6A,and 6B as appropriate.

2.1 Step S01: Production of Multi-layer Unit

In Step S01, an unsintered multi-layer unit 16 is produced.Specifically, first, a plurality of unsintered dielectric green sheetson which the first and second internal electrodes 12 and 13 are printedwith predetermined patterns as appropriate are laminated. Subsequently,the laminated dielectric green sheets are cut in the X- and Y-axisdirections for singulation, so that an unsintered multi-layer unit 16 isobtained.

FIG. 5 is a perspective view of the unsintered multi-layer unit 16obtained in Step S01. In the multi-layer unit 16, the surfaces S areformed as cut surfaces, and both the first internal electrodes 12 andthe second internal electrodes 13 are exposed at the surfaces S. Inother words, in the multi-layer unit 16 obtained in Step S01, thepositions of the end portions of the first and second internalelectrodes 12 and 13 in the Y-axis direction are aligned with oneanother in the surfaces S.

2.2 Step S02: Sintering

In Step S02, the unsintered multi-layer unit 16 obtained in Step S01 issintered. A sintering temperature for the multi-layer unit 16 can be setto approximately 1,000 to 1,300° C., for example, when a barium titanate(BaTiO₃) based material is used. Further, sintering can be performed ina reduction atmosphere or a low-oxygen partial pressure atmosphere, forexample.

In such a manner, in this embodiment, the multi-layer unit 16 issintered before the side margins 17 are formed in Step S03 to bedescribed later. This can remove a solvent or a binder contained in theunsintered multi-layer unit 16 more reliably. Therefore, in thisembodiment, it is possible to produce a multi-layer ceramic capacitor 10with a stable quality.

2.3 Step S03: Formation of Side Margins

In Step S03, the side margins 17 are provided to the side surfaces S ofthe multi-layer unit 16 sintered in Step S02, to produce a ceramic body11. Specifically, in Step S03, the unsintered side margins 17 areprovided to the side surfaces S of the multi-layer unit 16 by dippingand then baked onto the surfaces S of the multi-layer unit 16.

More specifically, first, as shown in FIG. 6A, ceramic slurry SL housedin a container is prepared, and one side surface S of the multi-layerunit 16, the other side surface S of which is held with a tape T, iscaused to face the ceramic slurry SL. The thickness of the side margin17 is adjustable by the contained amount of a solvent or a binder in theceramic slurry SL.

Next, the multi-layer unit 16 shown in FIG. 6A is moved downward andthen the side surface S of the multi-layer unit 16 is immersed into theceramic slurry SL. Subsequently, as shown in FIG. 6B, the multi-layerunit 16 is pulled up in a state where the ceramic slurry SL is adheringto the surface S. Thus, the unsintered side margin 17 is formed on thesurface S of the multi-layer unit 16.

Subsequently, the orientation of the side surface S of the multi-layerunit 16 in the Y-axis direction is inverted by transferring themulti-layer unit 16 to a tape different from the tape T shown in FIG.6B. In the manner similar to the above, the unsintered side margin 17 isformed also on the side surface S on the other side of the multi-layerunit 16, on which the side margin 17 is not formed.

The multi-layer unit 16 having the surfaces S on which the unsinteredside margins 17 are formed is then re-sintered. Thus, the side margins17 are sintered and are simultaneously baked onto the surfaces S of themulti-layer unit 16. Thus, the ceramic body 11 of the multi-layerceramic capacitor 10 is obtained.

When the side margins 17 are baked, stress corresponding to a shrinkagebehavior of the side margins 17 is applied between the multi-layer unit16 and the side margins 17. This stress is likely to increaseparticularly in a large-size multi-layer ceramic capacitor 10. Thisstress may cause the side margins 17 to be peeled off from the surfacesS of the multi-layer unit 16.

In this regard, the side margins 17 according to this embodiment areformed by dipping into the ceramic slurry SL, and thus the side margins17 has flexibility in the unsintered stage. Accordingly, the stress tobe applied between the multi-layer unit 16 and the side margins 17 dueto the shrinkage of the side margins 17 at the time of baking issuppressed. Thus, the peel-off of the side margins 17 is less likely tooccur.

It should be noted that a method of providing the unsintered sidemargins 17 to the surfaces S of the multi-layer unit 16 is not limitedto the dipping. For example, a ceramic sheet may be used instead of theceramic slurry SL. In this case, the side margin 17 may be formed on thesurface S of the multi-layer unit 16 by punching the ceramic sheet bythe surface S of the multi-layer unit 16.

Alternatively, the unsintered side margins 17 may be provided to thesurfaces S of the unsintered multi-layer unit 16 before Step S02 asneeded, to form the unsintered ceramic body 11. With this configuration,in Step S02, the multi-layer unit 16 and the side margins 17 that formthe ceramic body 11 can be simultaneously sintered.

2.4 Step S04: Formation of External Electrodes

In Step S04, the first external electrode 14 and the second externalelectrode 15 are formed on both the end portions of the ceramic body 11in the X-axis direction obtained in Step S03, to produce the multi-layerceramic capacitor 10 shown in FIGS. 1 to 3. A method of forming thefirst external electrode 14 and the second external electrode 15 in StepS04 is optionally selectable from publicly known methods.

3. DETAILED CONFIGURATION OF PROTECTIVE UNIT 20

3.1 Thickness of Side Margin 17

In the methods in the related art in which the side margins are notsubsequently provided, internal electrode patterns are printed on theunsintered dielectric green sheets to form the side margins. In otherwords, the internal electrodes are disposed to be spaced from the cutsurface, which is obtained at the time of singulation, with a gapcorresponding to each side margin. Therefore, a ceramic body includingthe side margins is obtained at the time of singulation.

In the above-mentioned methods in the related art, there is a limitationon the position accuracy of the printing and lamination of the internalelectrodes, and thus the internal electrodes are misaligned with oneanother. As a result, the thickness of the side margin is likely to bedeviated from a design value. For that reason, in order to appropriatelyprotect the internal electrodes, the thickness of the side margin isinevitably designed to be large in consideration of the misalignment ofthe internal electrodes.

To the contrary, as described above, in the method of producing themulti-layer ceramic capacitor 10 according to this embodiment, thepositions of the end portions of the first and second internalelectrodes 12 and 13 in the Y-axis direction are aligned with oneanother in the surfaces S of the multi-layer unit 16. Specifically, thepositions of the end portions of the first and second internalelectrodes 12 and 13 in the Y-axis direction are aligned with oneanother in the range of 0.5 μm in the Y-axis direction.

In this embodiment, the side margins 17 are provided in a subsequentstep on the side surfaces S of the multi-layer unit 16 in which the endportions of the first and second internal electrodes 12 and 13 in theY-axis direction are aligned with one another as described above. Withthis configuration, in the multi-layer ceramic capacitor 10 according tothis embodiment, the thickness of the side margin 17 is less likely tobe deviated from the design value.

Accordingly, in the multi-layer ceramic capacitor 10, the thickness ofthe side margin 17 can be determined without considering such designerrors that may occur in the production methods in the related art.Therefore, in the multi-layer ceramic capacitor 10, the side margin 17can be set to have the minimum thickness in a range where the firstinternal electrodes 12 and the second internal electrodes 13 can beappropriately protected.

Therefore, in the multi-layer ceramic capacitor 10, the thickness of theside margin 17 can be reduced to enlarge the dimensions of the firstinternal electrodes 12 and the second internal electrodes 13 in theY-axis direction as much. With this configuration, in the multi-layerceramic capacitor 10, the intersectional area of the first internalelectrodes 12 and the second internal electrodes 13 can be enlargedwithout involving increase in size.

In such a manner, even if the multi-layer ceramic capacitor 10 achievesthe increase in capacitance, the weight is not increased, that is, animpact to be given by the self-weight when the multi-layer ceramiccapacitor 10 drops is not increased. Thus, a crack is less likely to begenerated. Therefore, in the multi-layer ceramic capacitor 10 accordingto this embodiment, both of high moisture resistance and a largecapacitance can be obtained.

In the multi-layer ceramic capacitor 10, it is favorable to suppress themaximum thickness of the side margin 17 to be 50 μm or less from theviewpoint of the increase in capacitance. Further, in the multi-layerceramic capacitor 10, it is favorable to ensure 30 μm or more for themaximum thickness of the side margin 17 from the viewpoint of theperformance for protecting the first and second internal electrodes 12and 13.

3.2 Ridge 20 a of Protective Unit 20

As shown in FIG. 3, four ridges 20 a extending in the X-axis directionare formed in the protective unit 20 of the multi-layer ceramiccapacitor 10. Each of the ridges 20 a of the protective unit 20protrudes outward, and is thus likely to receive an external impact.From the viewpoint of mitigating the external impact, the ridges 20 a ofthe protective unit 20 are favorably rounded by chamfering or the like.

FIG. 7 is a partially enlarged cross-sectional view of a region V of themulti-layer ceramic capacitor 10, which is surrounded by a chain line ofFIG. 3. In other words, FIG. 7 shows the vicinity of the ridge 20 a ofthe protective unit 20. It should be noted that FIG. 7 shows one of thefour ridges 20 a, but all of the four ridges 20 a have the similarconfiguration.

FIG. 7 shows a shortest distance D from an end portion E of theoutermost layer in the Y-axis direction, the outermost layer beinglocated outermost in the first and second internal electrodes 12 and 13in the Z-axis direction, to the outer surface of the protective unit 20including the cover 19 and the side margin 17. In other words, theshortest distance D represents the smallest thickness of the protectiveunit 20 in the vicinity of the end portion E of the outermost layer inthe first and second internal electrodes 12 and 13, the end portion Ebeing adjacent to the ridge 20 a of the protective unit 20.

In the multi-layer ceramic capacitor 10, the thickness of the protectiveunit 20 is ensured to be larger than the length of the shortest distanceD in the vicinity of the end portion E of the outermost layer in thefirst and second internal electrodes 12 and 13. In this embodiment, theshortest distance D is larger than 10 μm. With this configuration, evenif a crack is generated in the ridge 20 a of the protective unit 20, thecrack is less likely to reach the end portion E of the outermost layerin the first and second internal electrodes 12 and 13.

Accordingly, in the multi-layer ceramic capacitor 10, moisture that hasinfiltrated into the crack generated in the ridge 20 a of the protectiveunit 20 is less likely to reach the first and second internal electrodes12 and 13. Therefore, in the multi-layer ceramic capacitor 10, theinsulation properties between the first internal electrodes 12 and thesecond internal electrodes 13 are less likely to be impaired by themoisture, and thus high moisture resistance is obtained.

The effect of high moisture resistance by the protective unit 20 isobtained effectively in the multi-layer ceramic capacitor 10 with theweight of 8 mg or more, more effectively in a multi-layer ceramiccapacitor 10 with the weight of 100 mg or more, and still moreeffectively in a multi-layer ceramic capacitor 10 with the weight of 300mg or more.

In the configuration shown in FIG. 7, a position of the outer surface ofthe protective unit 20, which has the shortest distance D from the endportion E of the outermost layer in the first and second internalelectrodes 12 and 13, is located at the rounded end portion of the sidemargin 17 in the Z-axis direction. However, the configuration of theprotective unit 20 is not limited to that shown in FIG. 7 and may bethose shown in FIGS. 8A to 8C, for example.

Compared to the configuration shown in FIG. 7, in the configurationshown in FIG. 8A, the first internal electrodes 12 and the secondinternal electrodes 13 are positioned inward in the Z-axis direction,and the thickness of the cover 19 in the Z-axis direction is large. Inthis configuration, a position of the outer surface of the protectiveunit 20, which has the shortest distance D from the end portion E of theoutermost layer in the first and second internal electrodes 12 and 13,is located at a flat portion of the outer surface of the protective unit20, which is located inward in the Z-axis direction relative to therounded end portion of the side margin 17.

Compared to the configuration shown in FIG. 7, in the configurationshown in FIG. 8B, the first internal electrodes 12 and the secondinternal electrodes 13 are disposed outward in the Z-axis direction, andthe thickness of the cover 19 in the Z-axis direction is reduced. Inthis configuration, a position of the outer surface of the protectiveunit 20, which has the shortest distance D from the end portion E of theoutermost layer in the first and second internal electrodes 12 and 13,is located at a connection portion of the cover 19 and the side margin17.

In the configuration shown in FIG. 8C, an extended portion 17 a isprovided to the side margin 17 shown in FIG. 8B. The extended portion 17a slightly extends to the main surface M from the surface S of themulti-layer unit 16. In this configuration, a position of the outersurface of the protective unit 20, which has the shortest distance Dfrom the end portion E of the outermost layer in the first and secondinternal electrodes 12 and 13, is located at a boundary portion betweenthe cover 19 and the extended portion 17 a of the side margin 17.

In any of the configurations shown in FIGS. 8A to 8C, the shortestdistance D is configured to exceed 10 μm, so that a crack generated inthe ridge 20 a of the protective unit 20 is less likely to reach the endportion E of the outermost layer in the first and second internalelectrodes 12 and 13 as in the configuration shown in FIG. 7. Thisprovides high moisture resistance to the multi-layer ceramic capacitor10.

4. EXAMPLES AND COMPARATIVE EXAMPLES

Examples and Comparative examples of the embodiment will be described.Examples and Comparative examples to be described below are merelyexamples for confirming the effects of the embodiment described above.Accordingly, the configuration of the embodiment described above is notlimited to the configurations of Examples. In Examples and Comparativeexamples, samples of the multi-layer ceramic capacitors mainlycontaining BaTiO₃ were produced by the production method describedabove.

In each of Examples 1 to 8 and Comparative examples 1 to 11, 1,000samples were produced. The samples are different in size and weight inthe range from 8 mg to 339 mg between those examples. Further, thesamples of Examples 1 to 8 have a configuration in which the shortestdistance D exceeds 10 μm, and the samples of Comparative examples 1 to11 have a configuration in which the shortest distance D is 10 μm orless.

Table 1 shows the size, the weight, and the shortest distance D of thesamples according to Examples 1 to 8 and Comparative examples 1 to 11.In the size of the samples according to Examples 1 to 8 and Comparativeexamples 1 to 11 shown in Table 1, a “length” represents a dimension inthe X-axis direction, a “width” represents a dimension in the Y-axisdirection, and a “thickness” represents a dimension in the Z-axisdirection.

TABLE 1 Shortest Size (mm) Weight distance D Length Width Thickness (mg)(μm) Example 1 1.6 0.8 0.8 8 11 Example 2 1.6 0.8 0.8 8 12 Example 3 2.01.25 1.25 26 11 Example 4 2.0 1.25 1.25 26 12 Example 5 3.2 1.6 1.6 7311 Example 6 4.5 3.2 2.5 253 11 Example 7 4.5 3.2 3.2 339 11 Example 84.5 3.2 3.2 339 12 Comparative 1.6 0.8 0.8 8 8 example 1 Comparative 1.60.8 0.8 8 9 example 2 Comparative 1.6 0.8 0.8 8 10 example 3 Comparative2.0 1.25 1.25 26 9 example 4 Comparative 2.0 1.25 1.25 26 10 example 5Comparative 3.2 1.6 1.6 73 9 example 6 Comparative 3.2 1.6 1.6 73 10example 7 Comparative 4.5 3.2 2.5 253 9 example 8 Comparative 4.5 3.22.5 253 10 example 9 Comparative 4.5 3.2 3.2 339 9 example 10Comparative 4.5 3.2 3.2 339 10 example 11

The samples according to Examples 1 to 8 and Comparative examples 1 to11 were caused to drop from a predetermined height and collide withsimilar samples separately prepared. Subsequently, a moisture resistanceload test was performed, in which the samples were held for 500 hours ata temperature of 40° C. and a humidity of 95%. For each of the samplessubjected to the moisture resistance load test, an electric resistancewas measured, and samples whose electric resistance has a value smallerthan 1 MΩ were determined as defective.

Tables 2 and 3 each show evaluation results of the moisture resistanceload test. Tables 2 and 3 each show collision energy to be applied tothe samples when the samples drop, and a failure rate that is a rate ofthe samples determined as defective in the moisture resistance loadtest. The collision energy (J) can be calculated as “(weight (kg))*(dropheight (m))*(acceleration of gravity (m/s²)) of each sample”.

Table 2 shows the failure rate in the moisture resistance load test, inwhich the drop height is 3 cm and which is performed for the samplesaccording to Examples 1 to 8 and Comparative examples 1 to 11. As shownin Table 2, no defective samples occurred in the moisture resistanceload test for all of Examples 1 to 8. Meanwhile, defective samplesoccurred in the moisture resistance load test for all of Comparativeexamples 1 to 11.

TABLE 2 Failure rate in Collision energy moisture resistance (J) loadtest Example 1 2.35E−06 0.0% Example 2 2.35E−06 0.0% Example 3 7.64E−060.0% Example 4 7.64E−06 0.0% Example 5 2.15E−05 0.0% Example 6 7.44E−050.0% Example 7 9.97E−05 0.0% Example 8 9.97E−05 0.0% Comparative example1 2.35E−06 0.2% Comparative example 2 2.35E−06 0.2% Comparative example3 2.35E−06 0.1% Comparative example 4 7.64E−06 0.1% Comparative example5 7.64E−06 0.2% Comparative example 6 2.15E−05 0.3% Comparative example7 2.15E−05 0.1% Comparative example 8 7.44E−05 0.2% Comparative example9 7.44E−05 0.1% Comparative example 10 9.97E−05 0.3% Comparative example11 9.97E−05 0.3%

Table 3 shows the failure rate in the moisture resistance load test, inwhich the drop height is 5 cm and which is performed for the samplesaccording to Examples 1 to 8 and Comparative examples 3, 4, 7, 10, and11. As shown in Table 3, no defective samples occurred in the moistureresistance load test for all of Examples 1 to 8. Meanwhile, defectivesamples occurred in the moisture resistance load test for all ofComparative examples 3, 4, 7, 10, and 11.

TABLE 3 Failure rate in Collision energy moisture resistance (J) loadtest Example 1 3.92E−06 0.0% Example 2 3.92E−06 0.0% Example 3 1.27E−050.0% Example 4 1.27E−05 0.0% Example 5 3.58E−05 0.0% Example 6 1.24E−040.0% Example 7 1.66E−04 0.0% Example 8 1.66E−04 0.0% Comparative example3 3.92E−06 0.2% Comparative example 4 1.27E−05 0.2% Comparative example7 3.58E−05 0.2% Comparative example 10 1.66E−04 0.4% Comparative example11 1.66E−04 0.4%

From those results, it is thought that cracks that may reach the firstand second internal electrodes 12 and 13 were not generated in theprotective units 20 of all the samples according to Examples 1 to 8.Meanwhile, it is thought that cracks that may reach the first and secondinternal electrodes 12 and 13 were generated in the protective units 20of all the samples, which have been determined as defective in themoisture resistance load test for Comparative examples 1 to 11.

FIG. 9A is a graph showing all the evaluation results of the moistureresistance load test. In FIG. 9A, the horizontal axis represents thecollision energy and the vertical axis represents the failure rate inthe moisture resistance load test. It is found that, as the collisionenergy becomes larger, the samples according to Comparative examplestend to have an increasing failure rate in the moisture resistance loadtest and cracks that may reach the internal electrodes are likely to begenerated in the protective units.

FIG. 9B is a graph in which the horizontal axis of FIG. 9A is changed tothe drop height. The drop height assumed in normal manufacturing ormounting is approximately 3 cm, or approximately 5 cm at a maximum.Accordingly, it is found that the samples according to Examples 1 to 8can effectively suppress reduction in moisture resistance, which iscaused by cracks generated when the samples drop in normal manufacturingor mounting.

Further, FIG. 9B also shows evaluation results in a moisture resistanceload test for small samples of the multi-layer ceramic capacitor, themoisture resistance load test being similar to that performed forExamples and Comparative examples. Specifically, the size of the smallsample was set to a length of 1.0 mm, a width of 0.5 mm, and a thicknessof 0.5 mm. Further, the small sample was set to have a weight of 2 mgand a shortest distance D of 10 μm.

In any of the small samples, defective samples were not generated in themoisture resistance load test even when the drop height was set to 10 cmand further 15 cm, which are much higher than that assumed in normalmanufacturing or mounting. Accordingly, it is considered that the smallsamples do not have cracks that may reach the internal electrodes in theprotective units, irrespective of the shortest distance D of 10 μm orless.

In this regard, in the small samples of the multi-layer ceramiccapacitor whose weight is less than 8 mg, even if the drop height islarge, the collision energy does not increase, and thus it is consideredthat the cracks are not likely to be generated. Accordingly, in thesmall samples whose weight is less than 8 mg, reduction in moistureresistance due to the generation of cracks is less likely to occur ifthe shortest distance D is not configured to exceed 10 μm.

What is claimed is:
 1. A multi-layer ceramic capacitor having a weightof 8 mg or more, comprising: a capacitance forming unit includinginternal electrodes that are laminated in a first direction and includeend portions, positions of the end portions in a second directionorthogonal to the first direction being aligned with one another withina range of 0.5 μm in the second direction; and a protective unit thatcovers the capacitance forming unit in the first direction and thesecond direction and includes an outer surface, a shortest distancebetween the outer surface and the end portion of an outermost layer inthe internal electrodes in the first direction exceeding 10 μm.
 2. Themulti-layer ceramic capacitor according to claim 1, wherein the outersurface of the protective unit has an exposure dimension of 1 mm or morein a third direction orthogonal to the first direction and the seconddirection.
 3. The multi-layer ceramic capacitor according to claim 1,wherein the number of lamination of the internal electrodes is 500layers or more.